In the history matching process, the reservoir model is adjusted by manipulating the physical properties attributed to grid-cells representing the reservoir model such as porosity, permeability, relative permeability, net-to-gross (NTG), and skin factors to manually match actual production data (e.g. oil, water, gas flow rate and bottom hole pressure (BHP)). In practice there are mainly two techniques to modify manipulate the physical properties of the grid-cells: 1) identify multipliers to history match, which may result in significant deviation from the geomodel, but convergence would be fast; or 2) generate new realizations of the physical property using the geomodel, which are constrained by streamline-based sensitivities. The latter technique is rigorous because it generates a history match that honors geomodeling constraints but, at the same time, convergence can be slow.
Manual history matching is often used for coarse reservoir models with only a few hundred thousand grid-cells and a few production wells. For larger reservoir models with dozens of production wells, however, manual history matching is extremely time consuming. Because manual history matching involves a trial and error approach, it often results in a match based on unrealistic geological features. To prevent a match based on such features as the reservoir model size increases, various assisted history matching (AHM) techniques have been identified. Many of the AHM techniques, however, do not integrate interaction between the geomodel and the reservoir model during the history matching process. For example, once the geomodel is built, properties around the production wells and the injection wells are modified in a sequential manner (e.g. by using multipliers to change reservoir properties by factors). AHM techniques therefore, do not guarantee that the reservoir model honors all realistic geomodeling constraints, namely variograms and well logs (e.g. permeability and facies).